Proceedings of the NHEXAS Data Analysis Workshop

Abstract:

The National Human Exposure Assessment Survey (NHEXAS) was developed by the Office of Research and Development (ORD) of the U.S. Environmental Protection Agency (EPA) early in the 1990s to provide critical information about multipathway, multimedia population exposure distribution to chemical classes. The first phase consisted of three pilot studies with the objective of (1) evaluating the feasibility of NHEXAS concepts, methods, and approaches for the conduct of future population-based exposure studies; (2) evaluating the utility of NHEXAS data for improved risk assessment and management decisions; (3) testing the hypothesis that the distributions of exposure given by modeling and extant data do not differ from the measurement-based distributions of exposure; (4) defining the distribution of multi pathway human exposures for a relatively large geographic area; and (5) stimulating exposure research and forging strong working relationships between government and nongovernment scientists. NHEXAS began before the enactment of the Government Performance and Results Act (GPRA), which was written to ensure accountability in the use of resources. Thus, we add a "new" objective in the form of hypothesis: NHEXAS approaches can be used to develop a "GPRA Report Card" on the efficacy of EPA's regulations to reduce exposure.

As described in the overview (Section 2), NHEXAS is unique and complex study of approximately 550 people in three areas of the United States. The data collection phase of NHEXAS was completed recently, the initial data analyses will be published shortly (see October issue of the Journal of Exposure Analysis and Environmental Epidemiology (JEAEE), Appendix 1), and the principal investigators have additional analyses under way (Appendix 1). During a September 1998 review, the Integrated Human Exposure Committee (IHEC) of EPA's Science Advisory Board (SAB) (U.S. EPA, 1999) praised the NHEXAS pilots and recommended several actions to ensure that as much benefit as possible is derived from this very rich database. One such action was to develop a strategy for completing the analysis of the NHEXAS pilot data. To those ends, a workshop was convened with the goal of obtaining a wide range of expert opinion on which research projects best would ensure the utility of the NHEXAS data. Section 3 provides an overview of the workshop, and as described therein, the workshop projects will be used as information in developing the ORD strategy for analysis of the NHEXAS pilot data.

The workshop was successful in developing and suggesting a relative priority for research projects that covered the range of potential data analyses, including those that will support future exposure assessments, advance the science of exposure analysis, demonstrate lessons learned, and become part of the development of multimedia, mulipathway exposure models. The project descriptions, categorized within the four research areas, are provide in Section 4.